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By guest author Sofia Green, Volunteer in the CDF Marine Invasive Species Team.

Before volunteering at the Center for Marine Biology at the Charles Darwin Research Station, I knew next to nothing about marine invasive species. I hadn’t realized the importance of this study for the long-term conservation of the Galapagos Marine Reserve, nor did I imagine the adventures it would take me on.

Invasive species are an increasing problem in areas with growing populations and tourism, as well as throughout the Islands. In Galapagos, marine invasive species have increased with the increase in boat traffic, which is in response to more settlers on the islands and the increase of visitors. Who can blame anyone for wanting to come here? The magic of the Galapagos Islands lures people in; it is like Disney World for biologists, full of wonders and discoveries to be made. Having partially grown up in Galapagos due to my parents’ work, I always considered the Islands to be extraordinary — and after my university studies, I couldn’t think of a better place to work with my conservation biology degree in hand.

During my first fieldwork outing, my team and I spent the day at Tortuga Bay, one of the most beautiful beaches in the Archipelago. I was excited to call it my office for the day. We were gathering data on Caulerpa racemosa, an invasive species of algae that is thought to have originated in Australia. It is one of the seven identified marine invasive species in the Galapagos Islands. This particular species has been spreading and is increasingly sighted in more locations around the Archipelago. Our mission was to map the cover of the algae on several beaches by photographing the seafloor in transects and comparing it to the results from the previous data collection during the warm season. Even after reading all about Caulerpa, I never imagined how widespread it would be.

As we entered the water, I was stunned, and not just due to the chilly water the cold season brings from the Antarctic. We encountered the algae almost immediately, a few meters from the shore; it was not hard to miss. Caulerpa nearly covered the entire beach and looked more like a giant blanket than individual alga fronds. It seems to have taken over in just a few years. A local fisherman from Santa Cruz couldn’t remember seeing the algae at all seven years ago.

I soon noticed, however, that the entire area, despite being covered by algae, was full of life. I found white tip reef sharks, sting rays, a hidden octopus, many colourful reef fish, marine turtles, brittle stars, tiny crustaceans, tunicates, nudibranchs, and many other marine organisms. It is still a beautiful place to snorkel and I was happy to see that the algae does not seem to be affecting the diversity of the species, at least not yet.

After a few more outings like this to Tortuga Bay and rockier ones to La Ratonera beach, known to local surfers for its waves, which entailed photographing the sea floor in large swells, my team had the data necessary to map the algae. This meant having to use the computer software R, which was an adventure by itself. Anyone who has used it knows it can be incredibly frustrating at first. Yet it felt incredibly fulfilling once I managed to create those maps, where you can visibly note the growth of Caulerpa between the Hot Season (January-June) of 2017 and the Cold Season (July-December) of the same year.

The Marine Invasive Species Team is just now starting to understand how this alga is behaving in the Islands and the rate at which it is spreading. It is important to continue this study to fully understand the impact it could have on local species and the ecosystem. Thanks to the support of Galapagos Conservancy, this study is possible — and with our new findings, we will be able to initiate actions to control or eradicate Caulerpa racemosa and, if all goes well, prevent the introduction of more marine invasive species.

Sofía M. Green Iturralde grew up alternating between life in the Galapagos and in mainland Ecuador. She is a graduate in Conservation Biology and Equine Sciences and is volunteering for a year in the Galapagos Islands before continuing postgraduate studies in Marine Biology. She is currently working with the Marine Invasive Species Team at the Charles Darwin Research Station.